Pneumatic tires have been suggested which contain built in polyurethane based sealant layers which can flow into a tire puncture hole for a purpose of resisting flow of tire inflation air through the tire puncture and to thereby promote a resistance of the pneumatic tire going flat by loss of tire inflation air. For example, see U.S. Patent Application Serial No. 2009/0078352.
Such polyurethane sealant layers may be formed, for example, by application of a pre-formed solid polyurethane based sealant precursor layer to an uncured rubber tire assembly and curing the tire assembly in a suitable mold at an elevated temperature in which the polyurethane sealant precursor is degraded to form a better built in polyurethane based sealant layer within the tire having tire sealing properties.
However, effectively splicing the ends of the solid polyurethane based sealant precursor together to form an annular solid sealant precursor layer for the tire construction presents a challenge, particularly since, for example, a splice created by overlapping ends of the polyurethane layer gives rise to an imbalance of the tire.
Accordingly, is it an important aspect of this invention to enhance the solid annular sealant precursor layer by eliminating the splicing of its ends altogether. This is accomplished by spin casting a liquid polyurethane based sealant precursor reaction mixture into a tubular form and allowing the liquid sealant precursor reaction mixture to react and create a solid pre-formed seamless tubular shaped polyurethane based sealant precursor. A section of the pre-formed seamless tubular solid sealant precursor is cut from the tube and applied as an annular solid polyurethane based sealant precursor layer in an uncured pneumatic rubber tire following which the tire assembly is cured at an elevated temperature during which the solid annular tire polyurethane based sealant precursor layer is degraded and thereby converted to a built-in polyurethane based tire sealant layer within the tire with better (e.g. more efficient) sealing ability (in its degraded polyurethane form) to seal against various tire puncturing objects.